Blastomycosis is a chronic systemic mycosis characterized by primary pulmonary infection, which in some cases is followed by hematogenous dissemination to skin and other organs.
The fungus is endemic to countries in Central America, North and South America, most notably Brazil, Argentina, Colombia, and Venezuela, in regions classified as subtropical mountain forests. Infection with P brasiliensis is usually subclinical; however, the fungus sometimes proliferates, causing severe disease.
Causes of North American Blastomycosis
North American blastomycosis is caused by the yeast-like fungus Paracoccidioides brasiliensis that is acquired by breathing in the spores of the fungus
B.dermatitidis infection acquired from inhalation of dust from soil, decomposed vegetation, or rotting wood. Asymptomatic primary pulmonary infection usually resolves spontaneously. Hematogenous dissemination may occur to skin, skeletal system, prostate, epididymis, or mucosa of nose, mouth, or larynx. Reactivation may occur within lung or in sites of dissemination.
Risk factors for dissemination: T cell dysfunction; advanced HIV disease.
Symptoms of North American Blastomycosis
Symptoms include ulcers in the mouth, larynx and nose, in addition to large, draining lymph nodes, cough, chest pain, swollen lymph glands, weight loss, and lesions on the skin, genitals, and intestines. There may also be lesions in the liver, spleen, intestines, and adrenal glands.
Diagnosis
Clinical suspicion, confirmed by culture of organism from skin biopsy, sputum, pus, urine.
Treatment
General Care Patients with mild to moderate acute pulmonary blastomycosis often can be followed without antifungal therapy, especially if the patient is improving at time of diagnosis. Patients with meningitis or acute respiratory distress syndrome are best treated in hospital with IV amphotericin B.
Intravenous Amphotericin B In life-threatening infections: amphotericin B, 120-150 mg/week with a total dose of 2 g in adults. New liposomal preparations are less toxic. After initial improvement, therapy can be continued on an outpatient basis, three times weekly.
Oral Antifungal Therapy In those whose infection is non-life-threatening and/or those unable to tolerate amphotericin B: Itraconazole, 200-400 mg/d for >2 months; ketoconazole (alternative), 800 mg/d.
Prevention
Because of the widespread extent of B.dermatitidis in endemic regions avoidance is not possible.
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